Reconcentration of diluted polymer solutions by full adsorption/desorptionprocedure: II. Desorption of macromolecules by a narrow pulse of displacer

Diluted polymer solutions can be effectively reconcentrated applying full a dsorption/desorption processes. Macromolecules from diluted solutions are q uantitatively retained within a bed of appropriate adsorbent. Next, the pol ymer is released by a high-strength desorbing liquid that is introduced int o the sorbent bed as a narrow pulse. To evaluate the above reconcentration procedure, medium-polarity polymers, mainly poly(methyl methacrylate)s of v arious molar mass distributions were chosen as model species. Nonporous sil ica was used as an adsorbent, toluene and chloroform as adsorbing liquids, and tetrahydrofuran as a desorbing liquid in an HPLC-like apparatus. The co ncentration profiles of both the desorbing liquid pulse and desorbed polyme r were monitored with the usual LC detectors. On-line size exclusion chroma tography was employed in selected cases to determine molar mass and molar m ass distribution of desorbed macromolecules. The effect of some experimenta l parameters on the reconcentration efficiency was elucidated, viz. the nat ure of the sample solvent-adsorbing liquid, flow rate of desorbing liquid, molar mass, molar mass distribution, and nature of reconcentrated polymer, as well as relations among the amount of the polymer to be reconcentrated a nd the volume of the desorbing liquid pulse. It is shown that very high rec oncentration factors can be readily obtained by the full adsorption-desorpt ion procedure if the experimental conditions are carefully optimized. (C) 1 999 John Wiley & Sons, Inc.